Obsessive-compulsive disorder (OCD) is an anxiety disorder characterized by recurrent or persistent thoughts, impulses, or images that are experienced as intrusive or distressing (obsessions), and repetitive behaviors or mental acts (compulsions) often performed in response to an obsession. Approximately 1-4% of children and adolescents are affected by OCD at some point during youth, and the disorder is characterized by broad impairments in academic, social, and family functioning. This paper reviews the nature of obsessive-compulsive symptoms as well as etiological explanations for the disorder. Additionally, the topic of evidence-based assessment and treatment of OCD is discussed, with a particular focus on cognitive-behavioral treatment. We conclude with a discussion of future directions for the field.